It can cost you a fortune in the summer. Trust me.
Do a lot of research ahead of time. Some of the mini-golf places run all day armbands. And Big Chief Go Cart/Coasters used to do the same thing.
Depending on how many days you want to stay at a water park & how many of you there are, it may be cheaper to buy armbands at Kalahari for a single day & stay at a smaller hotel like Holiday Inn Express.
The boat tours (upper dells is better) & ducks are both fun.
Circus World Museum is in Baraboo.
Big casino a mile out of town on south side.
There was a thread on here last week with places to eat in the Dells. Good recommendations.
There are about 4 major waterpark hotels, Wilderness, Mt. Olympus, Kalahari & Great Wolf. All nice.